package com.hmdp.service.impl;

import static com.hmdp.utils.RedisConstants.*;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import javax.annotation.Resource;

import org.springframework.data.geo.Distance;
import org.springframework.data.geo.GeoResult;
import org.springframework.data.geo.GeoResults;
import org.springframework.data.redis.connection.RedisGeoCommands;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.domain.geo.GeoReference;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.SystemConstants;

import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    //新建一个线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassThrough(id);
        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //缓存击穿-互斥锁
//        Shop shop = queryWithMutex(id);
        //缓存击穿-逻辑过期  需要对商品做预热，也就是先将活动商品存入redis中，没有查到缓存，则表示该商品没有做活动
//        Shop shop = queryWithLogicalExpire(id);
//        Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.MINUTES);
        if(shop == null){
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
    }

    /**
     *  缓存击穿解决方案-逻辑过期
     * @param id
     * @return
     */
//    public Shop queryWithLogicalExpire(Long id){
//        String key = CACHE_SHOP_KEY + id;
//        // 1.从redis查询商铺缓存
//        String shopJson = stringRedisTemplate.opsForValue().get(key);
//        // 2.判断是否存在
//        if (StrUtil.isBlank(shopJson)) {
//            // 3.存在，直接返回
//            return null;
//        }
//        //命中，将json序列化为对象
//        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
//        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
//        LocalDateTime expireTime = redisData.getExpireTime();
//        //判断是否过期
//        if(expireTime.isAfter(LocalDateTime.now())){
//            //未过期，直接返回店铺信息
//            return shop;
//        }
//        //已过期，重建缓存
////        缓存重建，获取互斥锁
//        String lockKey = LOCK_SHOP_KEY + id;
//        boolean isLock = tryLock(lockKey);
//        //判断互斥锁是否成功
//        if(isLock){
//            //成功，开启新的线程写入redis,返回数据
//            CACHE_REBUILD_EXECUTOR.submit(()->{
//                try{
//                    this.saveShopRedis(id,20L);
//                } catch(Exception e){
//                    throw new RuntimeException(e);
//                }finally {
//                    unlock(lockKey);
//                }
//            });
//        }
//        //失败，返回旧数据
//        return shop;
//    }


    /**
     * 缓存击穿解决方案-互斥锁
     * @param id
     * @return
     */
//    public Shop queryWithMutex(Long id){
//        String key = CACHE_SHOP_KEY + id;
//        // 1.从redis查询商铺缓存
//        String shopJson = stringRedisTemplate.opsForValue().get(key);
//        // 2.判断是否存在
//        if (StrUtil.isNotBlank(shopJson)) {
//            // 3.存在，直接返回
//            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
//            return shop;
//        }
//        // 判断命中的是否是空值
//        if (shopJson != null) { //shop ==""
//            // 返回一个错误信息
//            return null;
//        }
//        //实现缓存重建
//        // 4.不存在，根据id查询数据库
//        // 4.1 获取互斥锁
//        String lockKey = "lockKey:" + id;
//        Shop shop = null;
//        try{
//            boolean isLock = tryLock(lockKey);
//            if(!isLock){
//                //判断失败，休眠并重试
//                Thread.sleep(500);
//                return queryWithMutex(id);
//            }
//            //成功，再查存下是否有缓存
//            key = CACHE_SHOP_KEY + id;
//            shopJson = stringRedisTemplate.opsForValue().get(key);
//            if (StrUtil.isNotBlank(shopJson)) {
//                // 3.存在，直接返回
//                 shop = JSONUtil.toBean(shopJson, Shop.class);
//                return shop;
//            }
//            //没有，根据id查询数据库
//            shop = this.getById(id);
//            // 5.不存在，返回错误
//            if (shop == null) {
////                将空值写入redis
//                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
////                返回错误信息
//                return null;
//            }
//            // 6.存在，写入redis
//            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
//
//        }catch (InterruptedException e){
//            throw new RuntimeException(e);
//        }finally {
//            //释放锁
//            unlock(lockKey);
//        }
//        // 7.返回
//        return shop;
//    }


    /**
     * 缓存穿透解决方案
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        // 1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        // 判断命中的是否是空值
        if (shopJson != null) { //shop ==""
            // 返回一个错误信息
            return null;
        }
        // 4.不存在，根据id查询数据库
        Shop shop = this.getById(id);
        // 5.不存在，返回错误
        if (shop == null) {
//                将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
//                返回错误信息
            return null;
        }
        // 6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        // 7.返回
        return shop;
    }


//    private boolean tryLock(String key){
//        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.MINUTES);
//        return BooleanUtil.isTrue(flag);
//    }
//
//    private void unlock(String key){
//        stringRedisTemplate.delete(key);
//    }


    /**
     * 缓存击穿，逻辑过期方案。对热点key(热销商店）做缓存，在redis预热数据
     * @param id
     * @param expireSeconds
     * @throws InterruptedException
     */
    private void saveShopRedis(Long id,Long expireSeconds) throws InterruptedException {
        //查询店铺数据
        Shop shop = this.getById(id);
        Thread.sleep(200);
        //封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,JSONUtil.toJsonStr(redisData));
    }
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long shopId = shop.getId();
        if(shopId == null){
            return Result.fail("该商铺不存在");
        }
        //更新数据库
        this.updateById(shop);
        //删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY+shopId);
        return Result.ok("更新商铺信息成功");
    }

    @Override
    public Result queryShopByType(Integer typeId, Integer current, Double x, Double y) {
        //判断是否需要根据最近距离展示商店
        if(x == null || y == null){
            //不需要，直接返回数据
            // 根据类型分页查询
            Page<Shop> page = this.query()
                    .eq("type_id", typeId)
                    .page(new Page<>(current, SystemConstants.DEFAULT_PAGE_SIZE));
            return Result.ok(page.getRecords());
        }
        //需要，获取最近商店id
        //1 计算分页参数
        int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        int end = current * SystemConstants.DEFAULT_PAGE_SIZE;
        // 3.查询redis、按照距离排序、分页。结果：shopId、distance
        String key = SHOP_GEO_KEY + typeId;
        GeoResults<RedisGeoCommands.GeoLocation<String>> results = stringRedisTemplate.opsForGeo()
                .search(
                        key,
                        GeoReference.fromCoordinate(x, y),
                        new Distance(5000),//5km
                        RedisGeoCommands.GeoSearchCommandArgs.newGeoSearchArgs().includeDistance().limit(end)
                );
        if(results == null){
            return Result.ok(Collections.emptyList());
        }
        List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = results.getContent();
        if(list.size() <= from){
            //表示没有下一页，直接返回
            return Result.ok(Collections.emptyList());
        }
        // 分页查询.截取 from ~ end的部分
        List<Long> ids = new ArrayList<>(list.size());  //存放商店id
        HashMap<String, Distance> distanceHashMap = new HashMap<>(list.size()); //存放 商店 相隔距离
        list.stream().skip(from).forEach(result -> {
            //获取店铺id
            String shopIdStr = result.getContent().getName();
            ids.add(Long.valueOf(shopIdStr));
            //获取距离
            Distance distance = result.getDistance();
            distanceHashMap.put(shopIdStr,distance);
        });
        //根据id查询商店信息
        String idStr = StrUtil.join(",", ids);
        List<Shop> shops = query().in("id", ids).last("ORDER BY FIELD(id," + idStr + ")").list();
        for(Shop shop: shops){
            shop.setDistance(distanceHashMap.get(shop.getId().toString()).getValue());
        }
        // 返回数据
        return Result.ok(shops);
    }
}